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Diels–Alder Reaction Forming Cyclic Products: Stereochemistry

Diels–Alder Reaction Forming Cyclic Products: Stereochemistry

The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.

[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction

[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction

The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.

Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry

Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry

Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.

Thermal Electrocyclic Reactions: Stereochemistry

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...

Diels–Alder Reaction: Characteristics of Dienes

Diels–Alder Reaction: Characteristics of Dienes

The Diels–Alder reaction brings together a diene and a dienophile to form a six-membered ring. Both components have unique characteristics that influence the rate of the reaction.
Characteristics of the diene
Conformation
The simplest example of a diene is 1,3-butadiene, an acyclic conjugated π system. At room temperature, the molecule exists as a mixture of s-cis and s-trans conformers by virtue of rotation around the carbon–carbon single bond. Although the s-trans isomer is...

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Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

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Published on: November 9, 2019

灾难的分离催化剂.

Daniel Moser¹, Tanno A Schmidt¹, Christof Sparr¹

¹Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland.

|October 27, 2023

概括

此摘要是机器生成的。

这项研究探讨了催化剂控制的立体分离,用于创建复杂的分子. 它强调了双催化策略,以有效地获取各种立体异构体,包括基和基异构体.

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Published on: April 4, 2014

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Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

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Published on: November 9, 2019

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Published on: February 16, 2018

Retropinacol/Cross-pinacol Coupling Reactions - A Catalytic Access to 1,2-Unsymmetrical Diols

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科学领域:

有机化学有机化学
催化剂是一种催化剂.
立体选择性合成立体选择性合成

背景情况:

合成化学家在控制二聚体合成的相对立体化学方面面临着挑战.
双催化方法 (序列式,继电式,协同式) 为立体控制提供了有效的策略.

研究的目的:

在构建碳立体中心时讨论催化剂控制的 diastereodivergence.
探索在体系统和基体几何学控制中的应用.

主要方法:

展示催化剂控制的 diastereodivergence 的说明性示例的审查.
将概念转移到体和基系统.

主要成果:

催化剂控制使得 diastereomers 的立体分离合成成为可能.
双催化是有效控制多个立体的单位.
灾难性分离催化扩展到体和E/Z基.

结论:

催化剂控制的二聚变是一种有机合成中的强大策略.
双催化方法可以有效地获得多种类型的立体同位素.
这些原则适用于各种立体系统.